orgo mcat chp3

Region of space where an electron is most likely found

Atomic orbital

Model describing electron behavior as probability distributions

Quantum mechanical model

Orbitals describing electron position probabilities

Wavefunctions

Maximum number of electrons per orbital

Two

Rule stating no two electrons have identical quantum numbers

Pauli exclusion principle

Rule stating electrons fill lowest energy orbitals first

Aufbau principle

Rule stating electrons occupy degenerate orbitals singly before pairing

Hund’s rule

Quantum number describing energy level and orbital size

Principal quantum number (n)

Quantum number describing orbital shape

Azimuthal quantum number (l)

Quantum number describing orbital orientation

Magnetic quantum number (mₗ)

Quantum number describing electron spin

Spin quantum number (mₛ)

Possible values of spin quantum number

+1/2 and −1/2

Possible values of azimuthal quantum number

0 to n−1

Possible values of magnetic quantum number

−l to +l

Orbital shape corresponding to l = 0

s orbital

Orbital shape corresponding to l = 1

p orbital

Orbital shape corresponding to l = 2

d orbital

Orbital shape corresponding to l = 3

f orbital

Shape of an s orbital

Spherical

Shape of a p orbital

Dumbbell

Number of p orbitals per energy level

Three

Maximum electrons in an s subshell

Two

Maximum electrons in a p subshell

Six

Maximum electrons in a d subshell

Ten

Bond formed by head-on overlap of orbitals

Sigma bond

Bond formed by side-by-side overlap of p orbitals

Pi bond

Strength comparison of sigma and pi bonds

Sigma is stronger

Single bond consists of

One sigma bond

Double bond consists of

One sigma bond and one pi bond

Triple bond consists of

One sigma bond and two pi bonds

Region of high electron density between nuclei

Bonding orbital

Region of low electron density between nuclei

Antibonding orbital

Star symbol indicating antibonding orbital

Asterisk

Theory combining atomic orbitals into molecular orbitals

Molecular orbital theory

Condition for bond formation in molecular orbital theory

Bond order greater than zero

Formula for bond order

Bonding electrons minus antibonding electrons divided by two

Orbital formed from s–s overlap

Sigma s bond

Orbital formed from p–p overlap end to end

Sigma p bond

Orbital formed from p–p overlap side by side

Pi bond

Mixing of atomic orbitals to form new equivalent orbitals

Hybridization

Hybridization with four electron domains

sp3

Hybridization with three electron domains

sp2

Hybridization with two electron domains

sp

Geometry associated with sp3 hybridization

Tetrahedral

Ideal bond angle in sp3 geometry

109.5 degrees

Geometry associated with sp2 hybridization

Trigonal planar

Ideal bond angle in sp2 geometry

120 degrees

Geometry associated with sp hybridization

Linear

Ideal bond angle in sp geometry

180 degrees

Hybridization of carbon in alkanes

sp3

Hybridization of carbon in alkenes

sp2

Hybridization of carbon in alkynes

sp

Number of unhybridized p orbitals in sp2 hybridization

One

Number of unhybridized p orbitals in sp hybridization

Two

Type of bond formed by unhybridized p orbitals

Pi bond

Delocalization of electrons across multiple adjacent atoms

Resonance

Structures differing only in electron placement

Resonance structures

Actual structure representing delocalized electrons

Resonance hybrid

Effect of resonance on molecular stability

Increases stability

Effect of resonance on bond lengths

Bond lengths become equalized

Type of bonds that participate in resonance

Pi bonds

Example of resonance relevant to biology

Peptide bond partial double-bond character

Common MCAT hybridization trap

Counting lone pairs incorrectly

Common MCAT orbital trap

Confusing orbitals with electron shells

Common MCAT bonding trap

Thinking pi bonds allow free rotation